Alan Turing: The Enigma (75 page)

Mike Woodger was there when Alan’s official honour was announced in June. For his war service he was appointed to the
Order of the British Empire — standard for civil servants of the rank that he had officially held. The letters OBE were added to his office door, which made him furious, perhaps because he did not want to be asked what it was for, perhaps at the absurdity of advertising a token recognition. The King was ill, so the OBE medal, bearing the inscription Tor God and the Empire’, arrived by post. It was lodged in his tool-box.

Already by May, when Jim Wilkinson joined in work on the ACE design, it had reached a Version V. One difference was that this incorporated a hardware facility for conditional branching. It was quickly replaced by a transitional Version VI and then a Version VII. By this time Alan was devoting more attention to speed of operation than he had done in the original report, at the cost of more hardware. In Version VII enough equipment was added to make it possible for an instruction to have the effect of a complete arithmetical operation, taking two numbers from store, adding them, and putting the result back into store. Again in the interest of speed, it was necessary to program the instructions so that as far as possible each instruction would be leaving its delay line just as the previous one had been executed. Since different operations would take different lengths of time to complete, this made the construction of tables into a crossword-puzzle operation. It also led to a decision that every instruction should specify which instruction the ‘head’ was to take next, abandoning the idea of a natural stream of consecutive orders, flowing with only occasional interruptions. It also increased the length of the instruction words from thirty-two to forty pulses, again requiring more equipment. In Version VII each such operation would take forty microseconds, but it would then take another forty microseconds to assemble the next instruction in the control circuits. Again in the interest of speed, Alan wished to eliminate this period by duplicating part of the equipment so that each instruction could be assembled while the last was being performed.

It was entirely in line with his original report that as experience was gained with writing instruction tables, he should modify aspects of the hardware design. It was consistent, too, that he should sacrifice a certain amount of simplicity for the sake of greater speed. All the same, the assembling of actual components could not begin too soon for him; the paper ‘tables’ were intended for a real machine, not as theoretical exercises.

In this respect, however, development was very far from speedy. There was an overwhelming problem with the ACE project. This was that although the ν PL had a Radio Division, it did not have a single electronic engineer capable of appreciating, let alone implementing, Alan’s ideas. Back in December 1944, Womersley had told the Executive Committee that plans for new machines ‘could be put into effect only by cooperation between the
Division and certain industrial organisations – possibly along the lines of extra-mural development contracts.’ But no progress had been made towards making this cooperation possible. There was one solid medium-term possibility, that of having English Electric, a firm with which Darwin had connections, manufacture a machine to commercial standards. Its director, Sir George Nelson, had attended the March meeting. But it was not at all clear who was to do the immediate development work. This was no small impediment to the confident hope expressed in Alan’s report of being able to produce the equipment for the logical control within six months.

A further problem lay in the internal structure of the NPL. At Hanslope, Alan had worked happily with Don Bayley, putting their different kinds of skill together. In this respect the Delilah project had been practice for the ACE, for he would have liked to work in much the same way again, if on a larger scale. (He had vaguely suggested that Don himself should come to the NPL, but Don was not due for release until February 1947, and he also felt he was rather more than the ‘amplifier king’ that Alan said he would need.)

But the National Physical Laboratory did not encourage any such
ad hoc
, informal collaboration. Its division of labour drew a firm line between brain and hand. Alan was cast firmly in the role of the theoretical designer, and was not expected to know anything about practical engineering. The bureaucratic outlook of the NPL also showed in the form-filling and permission-seeking necessary for the requisition of equipment, Meanwhile, to make matters worse, the post-war chaos, presenting something akin to a black market in war surplus materials, called for the skills of the spiv in locating hardware of any kind. For these reasons, there was no immediate prospect of having engineers qualified to build the circuits, and there was no facility for Alan to conduct practical experiments himself.

There was a more general difficulty facing the ACE project. It was one analogous to the arrival of the Enigma information in 1940. Alan had poured out a decade’s worth of ideas into the lap of an organisation which had not been noted for innovation. In 1940 the cryptanalysts had naively expected that the government could take the deciphered messages and put them to good effect. In fact it had needed two years of painful adjustment before this could be done, even with all the pressure of war. Now again the cornucopian abundance of the ACE design would require a change in attitudes. But there was no precedent for it, and although the administrators talked knowingly about what was needed, they had no clear idea of how to proceed. There was no tradition of major innovation at the NPL, and the ACE project brought out the conservative and negative character of the institution. Just as in 1941, Alan was impatient and uncomprehending of the organisational inertia.

Nor, perhaps, did he appreciate that the very high priorities enjoyed by
Bletchley, and the willingness of other organisations to sacrifice their independence, could no longer be expected in 1946. Thus at Dollis Hill, while there was no question about the competence of the Colossus engineers, their director, Radley, did not attach great importance to the work being done on delay lines for the ν PL. The Post Office had manifold tasks of its own in connection with the wartime backlog, and there was now no higher authority, no national policy, to coordinate the priorities of the various state enterprises. Alan and Womersley made an official visit to Dollis Hill on 3 April 1946, and thereafter work began – but in a desultory way, with the effect of creating an unforeseen delay, and a sense of uncertainty as to direction.

Alan had written in his report about the possibility of using cathode ray tubes as a quite different kind of storage system, and it was probably at his prompting that on 8 May 1946 Womersley wrote to TRE with an enquiry about the state of research at the radar establishment into the use of such tubes for storage, explaining that it might ‘form a suitable alternative to, or possibly even an improvement on, the mercury delay line which we are at present intending to use in our automatic computing engine .. V The response was not unhelpful, and on 13 August Darwin was able to write to Sir Edward Appleton at the DSIR:
¹⁰

…As I told you Womersley was down at TRE to see whether they could do any work about the ACE machine. He tells me that it looks a most promising chance, and I think we should go ahead on it. Their lay-out for the job looks good, and I gather it appealed strongly to F.C. Williams as a job he would like to do, so that it should get a good chance. I am kicking myself for not having thought of it months ago as a possibility.

As to what comes next Womersley has got to use some tact in exploring how we stand with the Post Office who have started to give us help, which would be very good but that they are not in a position to plunge very deep. It will also be necessary to square TRE officially over priorities, and on this I should like to bring high power to bear if necessary, because we have got a splendid chance of jumping in ahead of America.

F.C. Williams was one of the top electronic experts at TRE, and he was enthusiastic not because he was interested in computing, which he was not, but because he was anxious to find peacetime applications for the electronic skills developed in wartime radar. In finding such applications he had a mind of his own, and had an option open to him that did not accord with Darwin’s ‘high power’. It derived from Manchester.

Newman had left Bletchley to become Professor of Pure Mathematics at Manchester University, taking Jack Good and David Rees with him as junior lecturers. (Rees was another of the 1939 Part III class, who had joined Welchman’s hut in December 1939, and later joined the Newmanry.) In moving from a Cambridge lectureship to a Manchester University chair, he was following Blackett, then Professor of Physics. Together they
constituted a formidable team, and one which did not see why Darwin should monopolise electronic computers. As the first reader of
Computable Numbers
and the co-author of the Colossus, Newman appreciated the potential of computers as well as anyone, and if he lacked Alan’s emotional thrust towards ‘building a brain’, and the experience of assembling components himself, he compensated with a greater skill in the art of the possible.

Writing to von Neumann
¹¹
on 8 February 1946, Newman had explained that he was

hoping to embark on a computing machine section here, having got very interested in electronic devices of this kind during the last two or three years. By about 18 months ago I had decided to try my hand at starting up a machine unit when I got out. It was indeed one of my reasons for coming to Manchester that the set-up here is favourable in several ways. This was before I knew anything of the American work, or of the scheme for a unit at the National Physical Laboratory. Later I heard of the various American machines, existing and projected, from Hartree and Flowers.

Once the NPL project was started it became questionable whether a further unit was wanted. My view was that in this, as in other branches of technology, basic research is wanted, which can go on without worrying about getting into production …

Newman’s intention was that

mathematical problems of an entirely different kind from those so far tackled by machines might be tried, e.g. testing out (say) the 4-colour theorem or various theorems on lattices, groups, etc. …

He explained that

Anyhow, I have put in an application to the Royal Society for a grant of enough to make a start. I am of course in close touch with Turing. After discussion with him, and hearing Hartree and Flowers, it seemed to me that if we start on ‘mathematical’ problems here, in the above sense, we ought to be able to manage with considerably less storage, though I have asked to the Royal Society to be prepared for something fairly substantial.

Newman’s application was for a grant to cover the capital cost and five years of salaries for an electronic computer.
¹²
The Royal Society set up a committee to investigate the application for a grant, consisting of Blackett, Darwin, Hartree, and two pure mathematicians, Hodge from Cambridge and Whitehead from Oxford. Darwin opposed it on the grounds that the
ACE was to serve the needs of the country. Womersley had expressed the particular fear that Newman would steal Flowers away from the ACE. But he was outvoted, for it was approved that there should be ‘a different type of machine’ for Newman’s project. On 29 May the Treasury allocated £35,000 to Newman. The rationale was that as ‘fundamental science’, his proposal fell into the orbit of the Royal Society, and did not conflict with the DSIR. It meant that a rather surprising breath of mathematical innocence was felt again, with a computer development not required for weaponry.

It so happened that Blackett knew F.C. Williams from before the war, when they had collaborated on an automatic curve-tracer for the differential analyser. Both Darwin and Newman, therefore, were looking to Williams to help them ‘jump in ahead of America’, and Darwin’s plan for a single national computer installation had already been undermined. The question of who was going to build the ACE remained unresolved while Williams decided between these suitors.

This incipient rivalry was further complicated by the fact that a third British electronic computer project was initiated in mid-1946. This was the brainchild of M.V. Wilkes, Alan’s fellow ‘B-star’ of 1934 who in 1945 had left wartime work at TRE to resume his position at the Mathematical Laboratory in Cambridge, of which he now became director. He was in touch with Womersley at once, but the ENIAC and EDVAC plans were secret until the spring of 1946, and only then could Hartree tell him about what he had seen in 1945. Hartree then also arranged for him to attend a course of lectures arranged by the ENIAC team at Philadelphia in July and August 1946.

This course at the Moore School, together with the reports issued by von Neumann’s group at the IAS, enjoyed very considerable influence upon the future development of computers. For one thing, it brought about the first federal funding for a machine on the lines of the EDVAC. A certain James T. Pendergrass represented the Navy’s CS AW, and reported back
¹³
upon the virtue of a universal machine, as opposed to the special purpose equipment which had ‘often proved to be expensive and time-consuming.’ (Presumably Travis had been given the same analysis a year earlier.) For another, it inspired Wilkes with great enthusiasm for putting his wartime electronic experience to work in building a British version of the EDVAC.

Alan, in contrast, remained unaffected by the American developments, and they by him. In growth as in conception they were independent. There was a little indirect contact between the ν PL and the American group. Hartree had made a visit to the ENIAC in the summer of 1946, being allowed to use it himself, and took with him a copy of the ACE report and a ‘third version’ of the ACE design.
¹⁴
But its programming ideas made no obvious impression upon the Americans.